The Federal Emergency Management Agency's flood insurance rate maps are used to set flood insurance rates, regulate development in flood plains, and let people know about the risk they face.

FEMA is wrapping up a five-year map modernization plan that had led to digital flood maps for 92 percent of the continental U.S. population, the National Research Council said in a report made public Friday. But even after $1 billion has been spent on the effort, only 21 percent of the population has maps which meet all of FEMA's data quality standards, said the study, which was requested by FEMA and the National Oceanic and Atmospheric Administration.

The report said that FEMA often produces maps from the U.S. Geological Survey National Elevation Dataset, but that more accurate maps are available using lidar, which measures elevation from lasers on aircraft.

Among its recommendations, the report calls on FEMA to increase its collaboration with federal, state and local agencies to acquire high-resolution, high-accuracy topographic data.

"FEMA has recently begun to support collection of lidar data along the Gulf Coast, but lidar data coverage over most inland areas is still sparse," the report says.

A FEMA spokesman, Butch Kinerney, said the report "validates a lot of the things we're doing, and have done, and gives us good recommendations for going forward. We're changing the way we're looking at maps."

In addition to upgrading the maps, the agency is also helping communities to write plans to prepare for all sorts of disasters, including floods, he said.

Asked if he agreed that better maps could save lives and property, Kinerney said that a lot depends on how local communities choose to use the improved information.

"If a community adopts it, yeah, I think there are going to be dramatic effects," he said. "If a community chooses not to adopt it, it could be for naught."

The report said that despite ongoing changes in the floodplain, "FEMA flood maps are not updated on a regular schedule. Requests for changes are made irregularly and physical map revisions are infrequent due to funding constraints."

The report also suggested that FEMA replace its one-dimensional model for calculating wave heights with a two-dimensional model. The council did credit the agency with encouraging "rapid advancements in coastal flood modeling and mapping" following Hurricane Katrina in 2005.

The National Research Council is part of the National Academies, an independent organization chartered by Congress to advise the government on scientific matters.